Configuration as a Modbus Master
MVI56-MCM
♦
ControlLogix Platform
Modbus Communication Module
ProSoft Technology, Inc.
Page 45 of 159
July 24, 2008
The length of this COP statement must now be 14. This will COP as many of the
MCM_Float_Data values required to occupy the MCM.Data.WriteData array for a
length of 14. This will take 7 registers, MCM_Float_Data[0]-[6], and place that
data into MCM.DATA.WriteData[0]-[13].
Here is the command that must be configured to write these 7 Floating Point
values.
Based on the IntAddress and the configuration within the MCM.CONFIG.ModDef
section for WriteStartReg and WriteRegCount, the data from the tag
MCM.DATA.WriteData[0]-[6] will be written to Modbus addresses 47001 to 47007
of the slave device node #1.
Note: A swap code may be required to put the data in the proper format for the slave device.
4.5
Command Control and Event Command
Command Control and Event Command are features for the module in the
master mode of operation that will allow the user to change the command
execution based on some conditions in ladder. The module goes through the
command list sequentially, for instance it looks at
MCM.CONFIG.Port1MasterCmd[0], and then after completing that command will
then execute MCM.CONFIG.Port1MasterCmd[1], then
MCM.CONFIG.Port1MasterCmd[2], etc… Command Control and Event
command give the user the ability to place a command directly to the top of the
command queue, interrupting the regular command list execution.
Typically, this can be used to issue a reset to a device on a once a day basis,
poll for end of hour data, or issue special commands on the startup of a process
or the changing of a batch.
Because these special command blocks will interrupt the normal polling list, it is
recommended that they are used sparingly, so that it does not interrupt your
normal data transfer. Special consideration must be used to make sure that the
data to be written to the device (on a Write command) has been placed into the
module database.
